The present invention relates to a computer system formed by a plurality of computers, and in particular to a method, and system, for allowing a plurality of computer systems to share the same storage device via mutually different interfaces.
In recent years, so-called downsizing is extensively conducted in the field of computer system. The business performed by mainframes in the past has recently been processed by open systems formed by personal computers and work stations.
It is now assumed that a computer is to access a disk device. Traditionally in mainframes, access to the disk device is conducted via an interface standardized so as to transfer a data record of count-key-data record format according to specification of a cylinder number, a header number and a record number (CCHHR). On the other hand, in open systems, access to the disk is conducted via an interface standardized so as to transfer a data block of fixed-sized block data record format according to specification of a logic block address (LBA).
This results in a problem that a disk device generally used in the mainframe cannot be accessed in the open system, and on the contrary, a disk device used in the open system cannot be accessed in the mainframe. Other storage devices such as a magnetic tape device cannot be shared between the mainframe and the open system, either.
Therefore, the user which makes the mainframe and the open system operate in parallel needs to produce individual backups of data respectively in the mainframe and the open system, store the backup data thus produced in separate storage media, and manage them. However, this is a heavy burden on the user""s operation. Since the open system is often added to an existing system including a mainframe, it is desirable to be able to backup data of the open system in a magnetic tape device or the like of the mainframe.
In xe2x80x9cData sharing unites mainframes with open systems,xe2x80x9d David Simpson, Datamation, February 1977, and xe2x80x9cNetworked storage speeds data access,xe2x80x9d Tim Quellette, Computerworld, Inc., November 1996, data sharing between mainframes and open systems is proposed, but concrete configurations for realizing it are not disclosed.
An object of the present invention is to provide a method, and system, for sharing storage devices such as disk devices among a plurality of computers respectively having different interfaces.
Another object of the present invention is to backup data of the open system on the mainframe side.
In accordance with the present invention, a method, whereby a first computer having an interface for accessing a data record of count-key-data format by specifying a CCHHR as an address and a second computer having an interface for accessing a data block of fixed-sized block record format by specifying a LBA as an address share a storage device via a storage device controller, includes making the shared storage device accessible with the CCHHR, creating predetermined dataset management information, and initializing data records of a data part in the count-key-data format, from the first computer; in response to a data block write request issued by the second computer, deriving the CCHHR of the data record included in the data part and mapped from the specified LBA with one-to-one correspondence, deriving a byte position with respect to head of the data record, and writing the data block onto the shared storage device; and in response to a data record read request issued by the first computer, reading a data record specified by a CCHHR from the shared storage device, and transferring the data record to the first computer.
Furthermore, in accordance with the present invention, the method for sharing a storage device via mutually different interfaces includes, in response to a data block write request issued by the second computer, writing a data block specified by a LBA onto the shared storage device, in response to a data record read request specifying a predetermined CCHHR assigned to dataset management information issued by the first computer, generating predetermined dataset management information, and transferring the predetermined management information to the first computer, and in response to a read request of a data record assigned to a data part issued by the first computer, deriving a LBA of a data block mapped from the specified CCHHR with one-to-one correspondence, reading a data record from the shared storage device by using the LBA, adding a generated predetermined count part to the data record thus read, and transferring resultant data to the first computer.
Furthermore, in accordance with the present invention, the method for sharing a storage device via mutually different interfaces includes, in response to a data record write request specifying a predetermined CCHHR assigned to dataset management device information issued by the first computer, converting the specified CCHHR to a LBA located outside an access range of the second computer and writing a data record of the dataset management information onto the shared storage device, in response to a data block write request issued by the second computer, writing a data block specified by a LBA onto the shared storage device, in response to a data record read request specifying a predetermined CCHHR assigned to dataset management information issued by the first computer, converting the specified CCHHR to a LBA and read predetermined dataset management information by using the LBA, adding a generated predetermined count unit to a data record of the dataset management information thus read and transferring resultant data to the first computer, and in response to a data record read request specifying a CCHHR assigned to a data part excepting dataset management information issued by the first computer, deriving a LBA of a data block mapped from the specified CCHHR with one-to-one correspondence, reading a data record from the shared storage device by using the LBA, adding a generated predetermined count part to the data record thus read, and transferring resultant data to the first computer.
Furthermore, in accordance with the present invention, the data record transferred from the shared storage device to the first computer as described above is written onto a separate storage device via the first computer, and whereby a backup of data on the shared storage device is created.
Owing to the present invention, the shared storage device can be accessed by both the open system and the main frame by using the conventional interface. In addition, data of the open system can be backed up on the main frame side owing to the present invention.